Data security for digital data storage

ABSTRACT

A computing system includes data encryption in the data path between a data source and data storage devices. The data encryption may utilize a key which is derived at least in part from an identification code stored in a non-volatile memory. The key may also be derived at least in part from user input to the computer.

RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 09/277,335,filed on Mar. 26, 1999, the entirety of which is hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods and apparatus for providing securityfor digital data stored on data storage media such as magnetic andoptical disks and tapes.

2. Description of the Related Art

Over the past several years, personal computing systems have become morepowerful, smaller, and less expensive. As this has occurred, more andmore computing applications are performed on personal computerplatforms. Local and wide area networks of personal computers are nowoften used in corporate and business applications instead of the largemainframes used for the same applications in the past. A further resultof the increases in performance and decreases in price of personalcomputers is a dramatic increase in personal computer use for householdfinancial and other sensitive and preferably confidential information.

The use of personal computers in these applications raises data securityand privacy issues which have thus far been insufficiently resolved.Laptop and other personal computers, as well as the removable datastorage media used in them are transported, mislaid, lost, and sometimesstolen. Consequently, security and privacy issues which were not presentwhen computers and their data storage media were generally fixed havenow become prominent. Administrators of computer resources in thebusiness environment must remain aware of the location of portablecomputing devices as well as the nature of the programs and data storedon them. For home users, concerns arise if credit card, social security,or bank account numbers are present on fixed or removable media whichmay be lost or stolen.

To resolve a few of these concerns, some programs allow the user topassword protect documents or files, thereby preventing access to thedata in the file unless the password is known. This provides limitedsecurity, however, since these schemes are easy to defeat with widelyavailable password extraction programs. Furthermore, although the act ofopening the file may be restricted in the relevant application program,the data itself resides on the media in raw form, and may still beextracted by a trained computer user.

Systems have also been proposed which perform encryption on data andapplication programs stored on tape and disk. These systems provideimproved security over the password protection described above. As oneexample, a system disclosed in U.S. Pat. No. 5,325,430 to Smyth et al.(incorporated herein by reference in its entirety) includes a securitymodule attached to a personal computer which performs data andapplication program encryption. The security module communicates with aremovable smart card assigned to a given user which contains encryptionkeys used by the security module. Although the security provided by thissystem is adequate for many applications, the circuitry used toimplement the system is complex, and administration of the system forproducing and assigning keys and smart cards is time consuming andexpensive.

Another system for encrypting files is disclosed in U.S. Pat. No.5,235,641 to Nozawa et al., the disclosure of which is also incorporatedherein by reference in its entirety. In this system, data stored to amagnetic tape is encrypted by a cryptographic adapter which is locatedin the data path between a host processor and a tape drive. In thissystem, the host processor generates cryptographic keys which are storedon the tape itself. This requires additional logic to encrypt the keysas well as the data, and consequently, this system requires relativelycomplex circuitry, and leaves the key potentially recoverable from thetape itself if the key encryption scheme is broken.

Thus, existing encryption systems for personal and portable computershave serious drawbacks, and have not been widely implemented. Inparticular, a system which is useful for an individual personal computeruser has not been heretofore provided. Such a system should provide datasecurity with flexibility and without expensive administration orimplementation.

SUMMARY OF THE INVENTION

In a computing system comprising host computing logic and at least onedata storage device, the invention comprises a method of data storagecomprising encrypting user generated data with an encryption process,wherein said encryption process is defined at least in part withinformation assigned to and associated with said host computing logic.

The invention may also comprise methods of making a computer. In oneembodiment, such a method comprises storing a hardware identifier in anon-volatile memory integrated circuit and installing the memoryintegrated circuit into said computer. The method may further compriseproviding a data path to data storage media, coupling a logic circuitcomprising an encryption engine to the data path, and connect a memoryintegrated circuit to the logic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a data storage system incorporating anembodiment of the invention.

FIG. 2 is a flow chart illustrating acts performed during key generationin an embodiment of the invention.

FIG. 3 is a block diagram illustrating an encrypting data path passingfrom a host processor to data storage devices, in accordance with oneembodiment of the invention.

FIG. 4 is a flow chart illustrating acts performed during key generationin another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described with reference to theaccompanying Figures, wherein like numerals refer to like elementsthroughout. The terminology used in the description presented herein isnot intended to be interpreted in any limited or restrictive manner,simply because it is being utilized in conjunction with a detaileddescription of certain specific embodiments of the invention.Furthermore, embodiments of the invention may include several novelfeatures, no single one of which is solely responsible for its desirableattributes or which is essential to practicing the invention hereindescribed.

Referring now to FIG. 1, a data storage system is illustrated whichincorporates aspects of the invention. The system includesencryption/decryption logic 10 that is connected to receive digital datafrom a data bus 12. The encryption/decryption logic 10 is configured toforward data received from the data bus 12 to data storage devices 14 inan encrypted form. The data or information transferred between the databus 12 and the data storage devices may comprise application programsthemselves, data used by application programs, or any other informationthat the host computing system stores to the data storage devices 14 ofthe system. As will be further explained below with reference to FIGS. 2and 3, the encryption/decryption logic may in some embodiments beconfigurable to perform the encryption and decryption on a selectablesubset of the data storage devices if desired by a user of the system.

The algorithm used to perform the encryption may comprise any knownencryption algorithm, and many different alternatives will be well knownto those of skill in the art. In many applications, the encryption anddecryption process will be defined in part by a key 16 which is utilizedby the encryption/decryption logic 10 to perform the data manipulationwhich results in data encryption and decryption. In some systems, thesame key is used for both the encryption and decryption processes, butin others, the key 16 may comprise a pair of keys, wherein one is usedfor encryption, and the other for decryption. Given the variety ofencryption and decryption schemes which have been and are currentlybeing developed, the use of the word “key” is intended to encompass anypiece of information, data, parameter, definition, configuration oflogic circuitry, or other entity or circuit arrangement which serves atleast in part to configure the encryption/decryption logic, or tootherwise in any way partly or wholly define the data encryption processwhich is performed by the encryption/decryption logic 10.

Also provided in the system of FIG. 1 is a non-volatile memory location18. As is well known in the art, a non-volatile memory has the propertythat the data or information stored in it remains when the host systemis powered down. Non-volatile memory may comprise battery backed up RAM,EPROM, EEPROM, or ROM memory circuitry, for example. In the applicationof FIG. 1, this memory location 18 may advantageously store anidentification code. The stored identification code may be used toderive, at least in part, the key 16 which is used in the encryptionprocess. This derivation may involve simply making the key theidentification code itself, or may alternatively involve a logical ormathematical manipulation or transformation of the identification codeto produce the key. In some embodiments, as will be further explainedbelow, the key 16 may be derived in part from the identification codestored in the non-volatile memory and in part from a password or otherpiece of information entered by a user of the computing system.

The system of FIG. 1 includes many advantages over prior art dataencryption schemes and is especially applicable to individual personalcomputer and laptop computer users. In some embodiments, the circuitryof FIG. 1 may be incorporated into, for example, a laptop computer whichis sold to an individual for household and/or business use. In most ofthese situations, the purchased computer will not be a member of a groupof computers which is controlled or overseen by a system administratorthat will create and assign encryption keys, smart cards, etc. Rather,the laptop will be simply used as is, for both personal and business useby a user who is generally unfamiliar with data security techniques orprocedures.

In these embodiments, the identification code may comprise a multi-bitdata word which is associated with the individual laptop being used.When stored in a non-erasable memory element such as ROM or EPROM, theidentification code may be substantially permanently associated with theindividual laptop being used. It will be appreciated that data securityin these environments is enhanced if different laptops do not typicallyshare a common identification code. When this is true, the key 16derived from the identification code will be different in differentlaptops produced by the laptop manufacturer. It will therefore also beappreciated that the data stored on the data storage devices 14 will beencrypted differently by different laptops. Thus, a removable media suchas a floppy disk, tape, or writeable CD will not be useable on anycomputer except the one that originally stored the data. Thus, a levelof security is provided for removable media which may be lost, mislaid,or stolen.

It will also be appreciated that this level of security is providedwithout any intervention by the user or a system administrator. Keygeneration and data encryption is automatic and transparent. Inaddition, this data security scheme is easily implemented in the largescale production of laptops and other personal computers. Machinespecific data encryption may be provided with the simple provision ofnon-volatile storage of information which defines the data encryptionprocess performed. This information may advantageously be substantiallyuniquely associated with the host computing logic or host computer. Thismay be ensured by using some form of sequential numbering scheme for theidentification code, or alternatively a random or pseudo-randomnumbering scheme with a low probability of producing two identicalidentification codes for different laptops. However, it may be notedthat it is not necessary to absolutely guarantee that each laptop have auniquely defined encryption process. The desirable feature is that therebe a relatively low probability that lost or stolen media will bereadable in some other laptop or personal computer available to someonewho has found or has stolen the media elements. Therefore, duplicateidentification codes and keys defining identical encryption processesmay be provided within a given set of computers while still maintaininga useful level of security. Thus, the association between identificationcodes and their respective host computers need only be substantiallyunique such that a reasonable level of security is created.

FIG. 2 illustrates a method of key generation and data encryptionaccording to one embodiment of the invention. It will be appreciatedthat the method shown in FIG. 2 may, in one embodiment, be implementedon hardware illustrated in FIG. 1.

The method begins at a start state 22, and moves from there to step 24,where an identification code is retrieved. The identification code maybe stored in a non-volatile memory, and may in addition be substantiallyuniquely associated with specific host computer hardware.

The system then moves to decision state 26, where it is decided whetheror not some user input should be utilized in the process of encryptionkey generation. If not, the method moves directly to step 28, where anencryption key is generated using the identification code retrieved atstep 24. If user input is to be used in key generation, the method movesfrom step 26 to step 30, where the user input is accepted by the system.The user input may, for example, comprise an alphanumeric code which istyped into the computer keyboard by the user in response to a systemprompt. Following this, the method moves to step 28, where the key isgenerated using both the identification code and the user input. Theuser input from step 30 may be an alphanumeric sequence which isconverted to a multi-bit word (for example, to ASCII code). This wordmay be combined with the identification code in many ways, includingconcatenation as one simple example, or other more complicated logicalor mathematical manipulations may be used.

Following key generation at step 28, the key is used to encrypt anddecrypt data that is stored to and retrieved from a data storage deviceat step 32. In the personal computer or laptop computer context, theseries of steps leading to and including key generation may be performedduring the boot operation prior to any accesses to encrypted datastorage devices. In these embodiments, all data, programs, etc. storedon the data storage devices are encrypted with the same key, a key whichmay require some user input to generate as described above. The computermay be either factory configured or user configured to require or notrequire user input for key generation.

The addition of user input to key generation provides an enhancement todata security beyond that provided when only the identification code isused to derive an encryption key. This is because if the entire computeris lost or stolen, when the computer is turned on only the computerowner will know what code or password to input in order to generate theproper key at step 28 of FIG. 2. Thus, access to encrypted programs anddata is effectively prevented even with the original computer the handsof an unauthorized user.

An embodiment of the invention is also illustrated in FIG. 3 which maybe used to implement the process described above with reference to FIG.2. In this Figure, a computer system is shown having a host processor36, which may, for example, comprise a member of the Pentium® family ofprocessors such as the Pentium, Pentium Pro, or Pentium II. Althoughindustry standard PC architecture is used as an illustrative example inthis Figure, it will be appreciated that many computer designs may beimplemented using the principles illustrated herein. Also provided aspart of the computer system of FIG. 3 are a plurality of data storagedevices, including hard disk drives 38, 40, a floppy disk drive 42 and aCD drive 46, which may be of a writeable type.

The processor 36 interfaces with a host bus 44 which also interfaceswith a bridge circuit 46. The bridge circuit 46 routes data from thehost bus 44 to a PCI bus 48. The PCI bus 48 provides a data source to alogic circuit 50 which is provided in the data path between the PCI bus48 and an IDE bus 52 and floppy drive control bus 54 which interfacedirectly with the respective data storage devices 38, 40, and 46. ThePCI bus 48 may also receive data from I/O devices 56 via a PCI to ISAbridge circuit 58.

The logic circuit 50 advantageously includes an encryption engine 60which operates to encrypt data routed to one or more of the data storagedevices 38, 40, 42, 46 and to decrypt data routed from one or more ofthe data storage devices 38, 40, 42, 46. The logic circuit 50 will alsogenerally include input and output bridge circuitry 51 to buffer dataand convert the data transfer protocol from the PCI format bus 48 to thebusses 52, 54, which interface directly with the data storage devices38, 40, 42, 46.

The encryption engine operates under the control of control logic 62.The control logic, in turn, receives information for controlling theencryption engine from three sources. The first is a memory locationwhich stores a hardware identifier 64. As described above, this hardwareidentifier 64 may be substantially uniquely associated with the computerhardware. The memory may comprise a non-volatile writeable or read onlymemory to help ensure essentially permanent storage of the hardwareidentifier 64. As is also described above, the hardware identifier 64stored in the memory may be used by the control logic 62 (oralternatively the processor 36) to at least in part derive a key forencryption and decryption of data to and from the data storage devices38, 40, 42, 46. The control logic may also accept user input asdescribed above to be used as additional information for key derivation.

This generated key may be stored in a key register 66 which also iscoupled to the control logic 62. Prior to data being stored or retrievedfrom the data storage devices 38, 40, 42, 46, the key may be retrievedfrom the key register 66 for use by the encryption engine 60 during theencryption and decryption processes.

A configuration register 70 may also be coupled to the control logic 62.The content of the configuration register 70 may advantageously be userdefined, and may include bits that determine which of the data storagedevices 38, 40, 42, 46 have data encrypted before storage to the media,and which have data decrypted when data is retrieved from the media.This feature provides significant flexibility to the user. A user may,for example, want to encrypt some, but not all, data stored onto afloppy disk with the floppy drive 42. It may also be advantageous tohave at least one hard drive 38 or 40, which contains DOS, Windows™,Unix™ or other operating system software, to remain unencrypted.

The configuration register may also contain bits which determine whetheror not user input should be incorporated into the key being used toperform the encryption and decryption. In some embodiments, a differentkey may be stored for different drives. In this case, some of the keysmay be generated with user input, and some without.

One advantageous aspect of the encryption system described herein isthat it may be created with relatively minor modifications to currentlyexisting integrated circuits. PCI to ISA and PCI to IDE bridges are wellknown and understood, and are commercially available from, for example,Intel Corporation. In one embodiment, therefore, an encryption engine,control logic, a key register, and a configuration register may beincorporated into an existing bridge integrated circuit design toproduce a portion of the logic circuit 50. Furthermore, individualEPROM, EEPROM and ROM memories which include pre-programmedidentification codes are available commercially from DallasSemiconductor of Dallas Tex. as part numbers DS2401 and DS2430 forexample. These devices include a unique 48 bit serial number in a ROMstorage location which may be utilized as the memory location whichstores the hardware identifier 64. These memory chips are available witha serial I/O interface for reading the identification code and any otherstored data. In this embodiment, therefore, a bridge integrated circuitwhich includes the encryption logic may interface over a serial bus to aseparate memory integrated circuit which stores the hardware identifier.

FIG. 4 illustrates a method of key generation and verification which maybe implemented with the system illustrated in FIG. 3. In the method ofFIG. 4, the control logic 62 (FIG. 3) may be utilized to perform keygeneration and verification without intervention by the processor 36(FIG. 3). The method begins at a start state 76. Following this startblock 76, the system retrieves the hardware identifier 64 (FIG. 3) fromthe non-volatile memory location where it is stored. This retrievalprocess may involve the sequential retrieval of a set of data words fromthe memory as illustrated by the loop defined by blocks 78, 80, and 82.Thus, at block 78, the control logic 62 may output an initial address tothe non-volatile memory to retrieve a first data word comprising aportion of the hardware identifier code 64. The address may then beincremented at block 80. If, at decision block 82, it is determined thatthe entire code has not yet been retrieved, the system loops back toblock 78 and outputs the incremented address to the non-volatile memoryto retrieve another segment of the code.

Once the entire code has been retrieved, at block 84 the control logic62 may then generate and verify the key. As mentioned above, the processof key generation may involve merely storing a concatenation of the datawords retrieved at steps 78-82 in the key register 66. This could occurduring the retrieval process, or afterwards. Alternatively, mathematicalor logical manipulations may be performed on the retrieved data wordsprior to their storage into the key register. Key verification may alsobe performed in a number of ways known to those of skill in the art. Forexample, a checksum or CRC field may be provided in the configurationregister 70 or control logic 62. If no user input is utilized in keygeneration, this field may be generated during an initializationsequence performed during the manufacture of either the logic circuit 50or a computer system that the logic circuit 50 is incorporated into. Ifuser input is utilized in key generation, this CRC or checksum field maybe generated during a password initialization routine when the passwordto be utilized in key generation is initially entered by the user.

Following key generation and verification, the system moves to adecision state 86, where the result of the key verification of block 84is checked. If the key is verified as good, the system moves to block88, and the key is used to encrypt and decrypt data during data storageand retrieval operations. There are several reasons why key verificationmight fail. An error in reading the hardware identifier may cause faultykey generation. Tampering with the logic circuit 50 may also result inincorrect key generation. Additionally, key verification may failbecause required operator input to be used in key generation has not yetbeen entered by a user. Thus, a failure of key verification may forceuser input. This is illustrated in FIG. 4 by the fact that if, atdecision state 86, the key has not been verified as good, the systemmoves to a another decision state 90. At decision state 90, the systemdetermines whether or not user input should be accepted and used in thekey generation process. If the system determines that operator inputshould be accepted, the system moves to block 92, where the input isread. The system then loops back to block 84, where the key is generatedusing both the operator input and the retrieved identification code, andis again verified against the stored CRC or checksum field. If theoperator input was the correct password, the key will be verified asgood at the next iteration of decision block 86, and at block 88, thekey will be used to encrypt and decrypt data as described above.

If, however, the operator input was incorrect, the key verificationprocess will fail, and the system will again move to decision state 90,where the system again determines whether or not user input should beaccepted. It will be appreciated that the user may be given two or moreattempts to successfully input the proper password. Thus, the system mayloop back to blocks 92 and 84 a plurality of times, any one of which mayresult in correct password entry and normal data encryption anddecryption at block 88.

After a selected number of iterations of incorrect password entry, thesystem may decide at state 90 to refuse to accept further operator inputfor key generation. In this event, the system moves to block 94 wherethe key error is flagged by the system. System response to the errorflag may vary widely. The system may indicate to the user that thepassword entries are incorrect. The system may even be programmed todestroy the content of encrypted drives in the event the keyverification process fails, or fails for a selected number ofconsecutive verification attempts.

The encryption system described thus provides data security to personaland laptop computer users in a transparent manner without requiring timeconsuming and expensive system administration or complex and expensivehardware. The system is especially adapted to individual users, and thehigh volume production of computers for these users.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated. The scope of the invention should therefore be construed inaccordance with the appended claims and any equivalents thereof.

1. In a personal computer having encryption hardware and a processor, amethod of storing data on data storage media comprising: retrievinginformation from a bus-to-bus bridge in a personal computer, theinformation identifying which data storage media are selected to receiveencrypted data; disabling encryption of data routed to one of the datastorage media in response to the retrieved information; encrypting anddecrypting data based on the disabling step, for storage on andretrieval from the data storage media; and storing the data in the datastorage media either in encrypted form or non-encrypted form based onthe disabling step.
 2. The method of claim 1, wherein encrypting datafor storage is performed on an encrypting device that is positioned in adata path between a central processing unit and the data storage media.3. The method of claim 2, wherein the bus-to-bus bridge comprises theencryption device.
 4. The method of claim 1, further comprisinggenerating a cryptographic key for use in encrypting the data.
 5. Themethod of claim 4, further comprising retrieving an identification code.6. The method of claim 5, wherein the retrieving the identification codeis performed without intervention by a host processor.
 7. The method ofclaim 4, wherein the cryptographic key is based at least in part on anidentification code stored in the personal computer.
 8. The method ofclaim 7, where the cryptographic key is based at least in part on userinput.
 9. The method of claim 4, further comprising verifying thegenerated cryptographic key, wherein verifying comprises determining achecksum of the generated key.
 10. The method of claim 9, wherein theverifying occurs without intervention of by a host processor.
 11. In apersonal computer having encryption hardware and a processor, a methodof storing data on data storage media comprising: retrieving informationfrom a bus-to-bus bridge in a personal computer, the informationidentifying which data storage media are selected to receive encrypteddata; encrypting data for storage on the data storage media selected toreceived encrypted data based on the retrieved information; and storingencrypted data on the data storage media selected to received encrypteddata.
 12. The method of claim 11, further comprising storing unencrypteddata on the data storage media not selected to received encrypted data.13. The method of claim 11, further comprising transmitting data from aprocessor in the personal computer to encryption hardware in thepersonal computer.
 14. The method of claim 11, wherein encrypting datafor storage is performed on an encrypting device that is positioned in adata path between a central processing unit and the data storage media.15. The method of claim 14, wherein the bus-to-bus bridge comprises theencryption device.
 16. The method of claim 11, further comprisinggenerating a cryptographic key for use in encrypting the data, whereinthe cryptographic key is based at least in part on an identificationcode stored in the personal computer.
 17. The method of claim 16,further comprising retrieving the identification code, wherein theretrieving the identification code is performed without intervention bya host processor.
 18. The method of claim 16, further comprisingverifying the generated cryptographic key, wherein the verifying occurswithout intervention of a host processor.
 19. A method of making acomputer comprising: storing a hardware identifier in a non-erasablememory integrated circuit; installing the non-erasable memory integratedcircuit into a computer; providing a data path to data storage media;providing a bus-to-bus bridge configured to store information, theinformation identifying which data storage media is selected to receiveencrypted data; coupling a logic circuit comprising an encryption engineto the data path; and connecting the non-erasable memory integratedcircuit to the logic circuit, wherein the hardware identifier and a userinput are used by an encrypting engine for encrypting data that istransmitted to the data storage media and for decrypting data that isretrieved from the data storage media, wherein the encryption engine isconfigured to disable encryption of data routed to the data storagemedia in response to the information.
 20. The method of claim 19,wherein connecting comprises routing a serial data bus from thenon-erasable memory integrated circuit to the logic circuit.